(Chapter 25) Footnote 35:

Vesalius cites the second book of De usu partium in the margin, where see 3.131.9ff.: “...From this description, then, it would seem that the carpus is composed of seven bones in all, but if you will wait to hear the special discussion of [the pisiform bone] lying on the inner side of the carpus ... you will be thoroughly persuaded that it was better for the carpus to be composed of eight bones, neither more nor less.” (tr. May 1968, p. 136).